HTML5 offers developers a File API
with drag-and-drop support to make web apps behave a bit more like desktop apps. Provided you’ve got a modern web browser and are using a web app that supports it (Gmail
are among the hundreds that do), uploading files works just like moving files on the desktop — drag and drop them where you want them.
The key word there is files, though. Drag and drop a folder of files and you’re out of luck. Currently browsers just ignore folders dropped into them. Chrome, however, recently added folder support to its bag of drag-and-drop tricks. You’ll need to be using Chrome 21 or better (currently in the dev channel